DSpace Community: KAIST Dept. of PhysicsKAIST Dept. of Physicshttp://hdl.handle.net/10203/5242019-09-07T04:26:55Z2019-09-07T04:26:55ZMagnetic force theory combined with quasi-particle self-consistent GW methodYoon, HongkeeJang, Seung WooSim, Jae-HoonKotani, TakaoHan, Myung Joonhttp://hdl.handle.net/10203/2639732019-08-05T05:20:17Z2019-10-01T00:00:00ZTitle: Magnetic force theory combined with quasi-particle self-consistent GW method
Authors: Yoon, Hongkee; Jang, Seung Woo; Sim, Jae-Hoon; Kotani, Takao; Han, Myung Joon
Abstract: We report a successful combination of magnetic force linear response theory with quasiparticle self-consistent GW method. The self-consistently determined wavefunctions and eigenvalues can just be used for the conventional magnetic force calculations. While its formulation is straightforward, this combination provides a way to investigate the effect of GW self-energy on the magnetic interactions which can hardly be quantified due to the limitation of current GW methodology in calculating the total energy difference in between different magnetic phases. In ferromagnetic 3d elements, GW self-energy slightly reduces the d bandwidth and enhances the interactions while the same long-range feature is maintained. In antiferromagnetic transition-metal monoxides, QSGW significantly reduces the interaction strengths by enlarging the gap. Orbital-dependent magnetic force calculations show that the coupling between e(g) and the nominally-empty 4s orbital is noticeably large in MnO which is reminiscent of the discussion for cuprates regarding the role of Cu-4s state. This combination of magnetic force theory with quasiparticle self-consistent GW can be a useful tool to study various magnetic materials.2019-10-01T00:00:00ZTemperature dependence of magnetic resonance in ferrimagnetic GdFeCo alloysOkuno, TakayaKim, Se KwonMoriyama, TakahiroKim, Duck-HoMizuno, HayatoIkebuchi, TetsuyaHirata, YuushouYoshikawa, HirokiTsukamoto, ArataKim, Kab-JinShiota, YoichiLee, Kyung-JinOno, Teruohttp://hdl.handle.net/10203/2643272019-08-20T05:20:14Z2019-09-01T00:00:00ZTitle: Temperature dependence of magnetic resonance in ferrimagnetic GdFeCo alloys
Authors: Okuno, Takaya; Kim, Se Kwon; Moriyama, Takahiro; Kim, Duck-Ho; Mizuno, Hayato; Ikebuchi, Tetsuya; Hirata, Yuushou; Yoshikawa, Hiroki; Tsukamoto, Arata; Kim, Kab-Jin; Shiota, Yoichi; Lee, Kyung-Jin; Ono, Teruo
Abstract: We provide a macroscopic theory and experimental results for magnetic resonances of antiferromagnetically-coupled ferrimagnets. Our theory, which interpolates the dynamics of antiferromagnets and ferromagnets smoothly, can describe ferrimagnetic resonances across the angular momentum compensation point. We also present experimental results for spin-torque induced ferrimagnetic resonance at several temperatures. The spectral analysis based on our theory reveals that the Gilbert damping parameter, which has been considered to be strongly temperature dependent, is insensitive to temperature. We envision that our work will facilitate further investigation of ferrimagnetic dynamics by providing a theoretical framework suitable for a broad range of temperatures. (C) 2019 The Japan Society of Applied Physics2019-09-01T00:00:00ZStatus of the 25 T, 100 mm Bore HTS Solenoid for an Axion Dark Matter Search ExperimentGupta, RameshAnerella, MichaelCozzolino, JohnJoshi, PiyushJoshi, ShreshtPlate, StephenSampson, WilliamSong, HonghaiWanderer, PeterChung, WoohyunKim, JingeunKo, Byeong RokYoun, Sung WooSemertzidis, Yannis K.http://hdl.handle.net/10203/2623582019-08-06T07:20:04Z2019-08-01T00:00:00ZTitle: Status of the 25 T, 100 mm Bore HTS Solenoid for an Axion Dark Matter Search Experiment
Authors: Gupta, Ramesh; Anerella, Michael; Cozzolino, John; Joshi, Piyush; Joshi, Shresht; Plate, Stephen; Sampson, William; Song, Honghai; Wanderer, Peter; Chung, Woohyun; Kim, Jingeun; Ko, Byeong Rok; Youn, Sung Woo; Semertzidis, Yannis K.
Abstract: This paper presents the design and test results of the pancake coils for the 25 T, 100 mm bore solenoid that Brookhaven National Laboratory (BNL) is building for the Insti-tute for Basic Science (IBS) in Korea for an Axion dark matter search. The design is based on second generation (2G) High Temperature Superconducting (HTS) tape with no-insulation winding. The major challenges in the high field, large aperture solenoid are the large stresses and the quench protection. Moreo-ver, the design should be robust for reliable operation in a user facility environment. The paper will also present the construction and test results of two ∼100 mm bore double pancake coils creat-ing a peak field of up to ∼17 T and similar hoop stresses as will be in the 25 T solenoid. The coils were subject to several severe tests, including the simulations of large defects and extended quench studies at ∼4 K. The most striking part of these studies was the demonstration of how fast (a few hundred milliseconds) these coils can turn from the superconducting state to the normal state (quench or thermal runaway). This removes the past concerns of protecting high field HTS coils because of the low quench propa-gation velocities.2019-08-01T00:00:00ZInterpreting Intensity Speckle as the Coherency Matrix of Classical LightLee, Kyeo RehPark, YongKeunhttp://hdl.handle.net/10203/2643512019-08-21T09:20:39Z2019-08-01T00:00:00ZTitle: Interpreting Intensity Speckle as the Coherency Matrix of Classical Light
Authors: Lee, Kyeo Reh; Park, YongKeun
Abstract: We show that an intensity speckle can be directly interpreted as the properties of incident light amplitude, phase, polarization, and coherency over spatial positions. Revisiting the speckle-correlation scattering matrix method [Lee and Park, Nat. Comm. 7, 13359 (2016)], we successfully extract the intact information of incident light from an intensity speckle snapshot as the form of a coherency matrix. The idea is experimentally verified by introducing the peculiar states of light that exhibit uneven amplitude, phase, polarization, and coherency features. We also find substantial practical advantage of the proposed method compared to the conventional coherency matrix measuring techniques such as Stokes polarimetry. We believe this physical interpretation of an intensity speckle could open a new avenue to study and utilize the speckle phenomenon in vast sub fields of wave physics.2019-08-01T00:00:00Z